Cutaneous fungal infections Notes

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Malassezia (Tinea versicolor and Seborrhoeic dermatitis)

NOTES NOTES CUTANEOUS FUNGAL INFECTIONS GENERALLY, WHAT ARE THEY? DIAGNOSIS PATHOLOGY & CAUSES ▪ Noninvasive fungal infections of skin and its annexes ▫ Limited to stratum corneum ▫ Caused by human skin’s commensal flora LAB RESULTS ▪ Microscopic observation OTHER DIAGNOSTICS ▪ Clinical findings upon examination SIGNS & SYMPTOMS ▪ Skin pigmentation changes ▪ Characteristic lesions: macule, patch, scale, plaque ▪ Occasional pruritus TREATMENT MEDICATIONS ▪ Antifungal MALASSEZIA (TINEA VERSICOLOR & SEBORRHOEIC DERMATITIS) osms.it/malassezia PATHOLOGY & CAUSES ▪ Genus of yeast-like fungi ▪ Cause cutaneous infections ▪ Cutaneous commensal flora, mostly lipiddependent (thrive on human sebum), saprophytic (nutrients obtained from dead, organic matter), dimorphic (yeast, hyphal/ mycelial forms) 366 OSMOSIS.ORG TYPES Tinea versicolor ▪ Superficial cutaneous mycosis ▪ AKA pityriasis versicolor ▪ Most common causes: M. globosa, M. furfur, M. sympodialis ▪ Fungus produces azelaic acid → tyrosinase activity (activated by sunlight) → skin pigmentation changes → hypopigmented/ hyperpigmented macules, patches, plaques
Chapter 67 Cutaneous Fungal Infections Seborrheic dermatitis ▪ Chronic, inflammatory dermatitis ▫ Tends to flare, relapse ▫ Likely caused by Malassezia spp. ▪ Fungus produces acids, enzymes, oxygen radicals → cell damage → inflammatory response → erythema, greasy, yellowish scaling (range from mild, flaky to coarse, thick lesions) RISK FACTORS Tinea versicolor ▪ Most common ▫ Adolescents/young adults ▪ Excessive heat, humidity, perspiration, sunlight ▪ Immunosuppression Figure 67.1 Tinea versicolor on the abdomen. Seborrheic dermatitis ▪ Biphasic occurrence ▫ Infants (cradle cap), adolescents/adults ▪ Biologically-male > biologically-female individuals ▪ Comorbidities ▫ HIV/AIDS, Parkinson’s disease SIGNS & SYMPTOMS Tinea versicolor ▪ Characteristic skin changes ▫ Usually located on abundant sebaceous gland areas (torso, proximal extremities, face, neck) ▪ Light brown in light-skinned individuals; dark brown to gray-black in dark-skinned individuals ▪ Mild erythema, pruritus, scaling ▪ Lesions fail to tan with sun exposure Seborrheic dermatitis ▪ Characteristic skin changes ▫ Usually located on trunk (“petaloid pattern”), scalp (dandruff), eyebrows, eyelids, nasolabial folds, external auditory meatus, anogenital area ▪ Pruritus, erythema, blepharitis ▪ Tends to flare during stress, cold weather ▪ Infants: adherent yellowish scales primarily on vertex of scalp Figure 67.2 Seborrhoeic dermatitis affecting the nasolabial folds. DIAGNOSIS LAB RESULTS Tinea versicolor ▪ KOH preparation: microscopic observation → “spaghetti and meatballs” ▫ Spaghetti: hyphae ▫ Meatballs: yeast OSMOSIS.ORG 367
OTHER DIAGNOSTICS Tinea versicolor ▪ Wood’s lamp examination: yellow to yellow-green fluorescence Seborrheic dermatitis ▪ Clinical findings upon examination TREATMENT MEDICATIONS Tinea versicolor ▪ Topical agents: antifungal medications, selenium sulfide, zinc pyrithione ▪ Oral antifungal medications if nonresponsive 368 OSMOSIS.ORG Seborrheic dermatitis ▪ No known cure ▪ Chronic topical agent treatment: antifungal medications, corticosteroids, calcineurin inhibitors ▫ Other topical agents: selenium sulfide, zinc pyrithione, salicylic acid or coal tar (keratolytics) ▪ Oral antifungal agents if non-responsive

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